Proposal for addition of half stars Ken Shirriff Aug 4, 2016 Abstract Star ratings are commonly used in text and online to rate movies, products and businesses. Ratings often use half stars, but unfortunately Unicode does not include a half star. There is user demand for half stars in Unicode. This proposal requests four types of half stars: solid and outlined, with left and right half stars for RTL support. Introduction Star ratings are commonly used in text and online to rate everything from movies and hotels to mutual funds, Medicare plans, and car safety. Ratings often use half stars, but unfortunately Unicode does not include a half star. There is substantial user demand for half stars in Unicode. This proposal requests four types of half stars: solid and outlined, with left and right half stars for bidirectional support. Examples of star ratings Ratings with half-stars are commonly used online, for example Amazon product reviews: Google ratings: Goodreads.com book reviews: The half star is heavily used on movie review sites. Some examples follow, in several languages. bigpicturebigsound.com: Proposal for addition of half stars, 1 of 10 blu-ray.com bollywoodhungama.com: cinemaglitz.com: biosagenda.nl: rollingstone.com: rogerebert.com: theglobeandmail.com: Proposal for addition of half stars, 2 of 10 The government system for rating Medicare plans uses half stars, resulting in many plan documents with half stars. For example: Half stars are used in contexts as diverse as rating windows or global competition: RTL Simon Montagu provided the following example of half-stars in RTL text, published in Haaretz 2 November 2012. This shows that usage of half stars isn't limited to left-to-right languages. Note that the line of stars is reversed: the half-star is on the left and has the solid part on the right, opposite of left-to-right usage. User demand for the symbol Many people have asked online for Unicode half-stars, showing the user demand for this symbol. Stack Overflow has hundreds of questions about half stars, most of which would be solved by a Proposal for addition of half stars, 3 of 10 Unicode half star. Other examples are this discussion of Unicode stars with three comments asking for half-stars, a Yahoo answers thread asking for Unicode half-star, a question asking for Unicode half star, a Stack Overflow asking how to clip a Unicode star to get a half star, a user asking for a half-star to put in Excel, and a Stack Overflow discussion on half-stars that contains a rant about Unicode lacking this character. Several software workarounds have been developed to display half-stars without their presence in Unicode, such as a CSS solution and a JQuery solution using a special font The suggested glyphs From above, it can be seen that half stars are used in both solid and outlined forms. The four proposed glyphs are: LEFT HALF BLACK STAR RIGHT HALF BLACK STAR STAR WITH LEFT HALF BLACK STAR WITH RIGHT HALF BLACK The glyphs are based on 'BLACK STAR' ★ (U+2605) and 'WHITE STAR' ☆ (U+2606) with the appropriate half filled in. A typical use for these characters would be representing 3.5 of 5: (standard) (RTL language) (empty stars outlined) (empty stars outlined, RTL) HalfStarDemo.ttf is a public-domain demonstration font with these four stars as U+E000 through U+E003. An open-source web font with half stars (fa-star-half and fa-star-half-o by Font Awesome) is also available, but it lacks the RTL versions. Proposal for addition of half stars, 4 of 10 Properties The proposed properties for the new symbols are: 2BD8;LEFT HALF BLACK STAR;So;0;ON;;;;;Y;;;;; 2BD9;RIGHT HALF BLACK STAR;So;0;ON;;;;;Y;;;;; 2BDA;STAR WITH LEFT HALF BLACK;So;0;ON;;;;;Y;;;;; 2BDB;STAR WITH RIGHT HALF BLACK;So;0;ON;;;;;Y;;;;; Name: The names LEFT HALF BLACK STAR, RIGHT HALF BLACK STAR, STAR WITH LEFT HALF BLACK, STAR WITH RIGHT HALF BLACK are suggested. The names parallel LEFT HALF BLACK CIRCLE, CIRCLE WITH LEFT HALF BLACK, etc. These names follow the shape-based character naming guidelines of ISO/IEC 10646:2014 Annex L Guideline 1. Range: Miscellaneous Symbols and Arrows (2B00-2BFF), with proposed code points 2BD8-2BDB – the next available code points in the range. The symbols are suitable for the Basic Monolingual Plane (BMP); they are high utility due to the size of the community and their heavy use of the symbol. Code points in the Supplemental Multilingual Plane (SMP) are not recommended because these characters are likely to be used by a variety of mobile devices and apps, with variable levels of support for SMP characters. Collation: The stars are not part of an existing collating sequence and does not require a particular collation order. Bidi: Existing stars are in the “Other Neutrals” class, so half stars should probably use the ON bidirectional class. The half stars have the obvious mirrored counterparts, so they can be Bidi mirrored. However, similar characters such as LEFT HALF BLACK CIRCLE are not marked as mirrored. I'll leave it up to the Unicode experts to determine if Bidi Mirrored would be appropriate or not. Proposal for addition of half stars, 5 of 10 Property Suggested Value Code point 2BD8-2BDB Name LEFT HALF BLACK STAR RIGHT HALF BLACK STAR STAR WITH LEFT HALF BLACK STAR WITH RIGHT HALF BLACK General Category So Canonical Combining Class 0 Bidirectional Class ON Decomposition Type / Decomposition Mapping Numeric Type Numeric Value Bidi Mirrored Y? Unicode 1 Name ISO Comment Simple Uppercase Mapping Simple Lowercase Mapping Simple Titlecase Mapping Table 1: Suggested character properties for the half stars. The stars are uncased and have no special line-breaking behavior. The character is not meant for use in identifiers. It is not a white-space character and has no numeric value. It is not a combining character or punctuation. Potential issues Can an existing Unicode symbol be used? There are dozens of existing Unicode stars, but none function well as half stars. I've seen documents use workarounds such as ✮ (HEAVY OUTLINED BLACK STAR) or (★) (a star in parentheses) These workarounds are not good substitutes for a half star and usually require explanatory text. For example (Market segmentation, by Malcolm McDonald): The ½ symbol is sometimes used in place of the half star in contexts where a half-star image would be difficult to use, such as in text. A published example from Leonard Maltin's 2009 Movie Guide: Proposal for addition of half stars, 6 of 10 An interesting use of ½ for the half-star is in the tile of a journal paper: A major reason not to use ½ for a half star is it doesn't work well in an interactive setting. Replacing with when clicked works more smoothly than replacing with ½. What about other half-symbols for ratings? The question comes up in discussion: What if someone wants to use half-tomatoes or half-hearts? There's no demonstrated demand for other half-symbols, while half-stars are commonly used. I don't anticipate a flood of other half-symbols. For concrete evidence, a Google search for [unicode half] turns up a variety of related searches. All the Unicode symbols already exist except for “unicode half star”. This suggests there is a demand for the half star, but no other untapped demand for half characters. What about fancy styling? Some sites use colored stars - half yellow, half gray is popular. Other sites use highly decorative stars. I don't think Unicode should try to support these uses; sites can use images as they do now if they want more styling than is possible with characters. Why just half? What about quarters or 13%? Should other fractions be supported, opening a can of worms? There's no demonstrated demand for other fractions. The half-star is a very common rating symbol. Many systems (e.g. Amazon) display a numeric value such as 4.3, but round the displayed stars to the half-star. Use of other star fractions is very rare. One suggestion was to use a combining character to permit an arbitrary fraction to be applied to an arbitrary character. This would allow a 13% filled heart for instance. While very flexible, this would be a nightmare to implement. There is no evidence of demand for this. Proposal for addition of half stars, 7 of 10 Why not double the number of stars and get rid of halves? The suggestion sometimes comes up to use a scale of 0-10 stars, and then the half star won't arise. It was pointed out that this makes subitizing more difficult. That is, people can understand 4 stars at a glance, but larger numbers would require much slower counting. Conclusion Half stars are commonly used for ratings on websites and publications. There is user demand for half stars and the lack of Unicode support requires inconvenient workarounds. Looking at the Unicode Criteria for Encoding Symbols, the half stars are a good fit for addition to Unicode. They occur in running text. They have a well defined user community. Being able to search for half-stars in text would be useful. They will complete the class of star symbols already in the standard. Finally, they are letter-like in the sense that they often should match the surrounding font style. For these reasons, the four suggested half stars are proposed for addition to Unicode. Acknowledgments: Several people provided helpful feedback including Philippe Verdy, Garth Wallace, Asmus Freytag, Leo Broukhis, Ken Whistler, Tex Texin, Frédéric Grosshans, Jörg Knappen and ACJ Unicode.